TY - JOUR

T1 - Understanding the fermentation factors affecting the separability of fermented milk

T2 - A model system study

AU - Priyashantha, Hasitha

AU - Buldo, Patrizia

AU - Berg, Thilo

AU - Gilleladen, Christian

AU - Ipsen, Richard

PY - 2021

Y1 - 2021

N2 - The demand for high-protein fermented milk products is globally increasing. The effect of added starter culture, cutting pH and fermentation temperature on separability, i.e., how well curd and whey separate, were evaluated in a model system aiming to resemble Greek-style yoghurt. Skim milk was fermented with three commercial starter cultures at 39 degrees C or 43 degrees C to a pH of 4.45 or 4.60. Stirred fermented gels were concentrated to produce high-protein (similar to 10%) fermented milk. The starter culture influenced the microstructure as well as the association (interactions) between exopolysaccharides (EPS) with the surface of the protein aggregates. The high association of EPS increased the viscosity and gel strength of the fermented model gels and decreased the zeta potential, the amount of whey removed as well as the protein and total solids concentration in the white mass. Increased fermentation temperature (from 39 degrees C to 43 degrees C) resulted in increased particle size and zeta potential values when EPS-producing starter cultures were applied. Cutting pH did not influence the separability of fermented stirred gels. The presence of EPS and pronounced association with protein increased the particle size, negative surface charge and structural rigidity, establishing a more stable system with reduced separability.

AB - The demand for high-protein fermented milk products is globally increasing. The effect of added starter culture, cutting pH and fermentation temperature on separability, i.e., how well curd and whey separate, were evaluated in a model system aiming to resemble Greek-style yoghurt. Skim milk was fermented with three commercial starter cultures at 39 degrees C or 43 degrees C to a pH of 4.45 or 4.60. Stirred fermented gels were concentrated to produce high-protein (similar to 10%) fermented milk. The starter culture influenced the microstructure as well as the association (interactions) between exopolysaccharides (EPS) with the surface of the protein aggregates. The high association of EPS increased the viscosity and gel strength of the fermented model gels and decreased the zeta potential, the amount of whey removed as well as the protein and total solids concentration in the white mass. Increased fermentation temperature (from 39 degrees C to 43 degrees C) resulted in increased particle size and zeta potential values when EPS-producing starter cultures were applied. Cutting pH did not influence the separability of fermented stirred gels. The presence of EPS and pronounced association with protein increased the particle size, negative surface charge and structural rigidity, establishing a more stable system with reduced separability.

KW - Greek yoghurt

KW - EPS-producing culture

KW - Stirred gel

KW - Microstructure

KW - Fermentation

U2 - 10.1016/j.foostr.2021.100232

DO - 10.1016/j.foostr.2021.100232

M3 - Journal article

VL - 30

JO - Food Structure

JF - Food Structure

SN - 2213-3291

M1 - 100232

ER -